Exercise stimulates endogenous fat mobilization and oxidation and is an important component of therapy for obese persons. However, the effect of exercose on lipid metabolism in obese people is not well understood. The purpose of this study is to: 1) evaluate whole-body and regioal lipolysis during exercise in lean and obese women and 2) evaluate the effect of endurance exercise training on lipid mobilization and oxidation during exercise in lean and obese women.